Spark plug seals



I June 28, 1960 w F. EITEL SPARK iled NNNNNN OR x ATTORNEY fllnited States atentfi ice Pat nted June as, 1,960

2, 43 221 SPARK PLUG SEALS Walter F. Eitel, Grand Blanc,;Mi ch., assignor to General" Motors Corporation, Detroit, Micln, ,a corporation of Delaware Filed May 9, 1957, Ser. No. 658,062 Y s Qlai ns. clan-144 This invention relates to an-improvementin sparkplu gengine seal construction of the type wherein the spark'plug being formed in a manner well known in the art. The

sp rk pl ihes a lower de he pq t as embl by anannular groove formedjin thespark plug shell has integrally formed therewitha sealing portion adapted for cooperation with a tapered seating surface formed in the engine cylinder head. More particularly, the invention relates .to incorporation in such seal structure of means to protect the spark plug sealing portion from nicks, abrasion or the like and constitutes an improvement in spark plug seal construction covered by copending United States patent application Serial No. 576,607,

filed April 6, 1956, in the name of Wilfred A. Bychinsky.

As will be more apparent from the description which follows, the efficiency and quality of spark plug seals of the aforementioned type are dependent upon the sealing portion of the spark plug being perfectly smooth and therefore adapted for intimate and unbroken contact with the tapered seating surface formed in the engine cylinder head. Difficulties have been encountered in obtaining uniformly effective seals with construction as covered by the aforementioned copending patent application because of nicks, burrs, abrasions and the like which frequently occur on the spark plug sealing portion during manufacturing and handling operations. Even slight scratches or nicks on the sealing portion can result in broken rather than unbroken contact between the spark plug and the engine cylinder head and thus can give rise to gas leakage and a poor seal.

It is an object of the present invention to provide improved spark plug seal construction which is simple and inexpensive and yet which assures in all instances a uniformly good seal. More specifically, it is an object of the invention to provide a spark plug seal construction wherein the spark plug seal is formed With an annular sealing portion adapted for unbroken intimate contact for a seating surface formed in the engine cylinder head and wherein means is provided on the spark plug for protecting the sealing portion thereof against unauthorized abrasion of any kind during manufacturing and handling operations. Still another object of the invention is the provision of an improved method for manufacturing spark plugs of a type having the seal formed integral with the spark plug shell, the key feature and advantage of which is the prevention of damage to the seal during manufacturing operations.

Other objects, advantages and features of the invention will appear more clearly from the following description of a preferred embodiment thereof and from the drawings in which:

Figure 1 is a side view in partial section of the spark plug seal construction embodying the invention; and

Figure 2 is a side view in section of the seal construction shown in Figure l, but in larger scale.

Referring now to Figure 1, there is shown a spark plug comprising a generally tubular metal shell 3 having a conventional ground electrode 4 welded or brazed there to and having concentrically secured therewithin an insulator-center electrode subassembly 5, this subassernbly just above the sealin'g portion such that said portion is provided with a relatively narrow cross sectional a'rea 15 a its ut end a is the e r ada t d bc e a t cally deflected an wa a ca ti e e t r ngrl ke. em e whe subjected at its end' section to force bywayofitseonta w that n u a e '11 a the spar plu .isthre ded 'into the engine bore. This cantilever action provides for a closer, more intimate contact between the outer circumferential sealing edgesurface of portion 13 and the seating surface 11. I

' Thus far ,the structure as described is the same as that covered by United States patent application Serial No. 576,607, referred to .above.

'It will be clear that with such structure, the elfectiveness of the seal between the spark plug and the engine cylinder head is dependent upon the surface, and particularly the outer edge, of sealing portion 13 being perfectly smooth and free of nicks, scratches, burrs or other abrasion. As mentioned above, it has been found that even small abrasions greatly reduce the quality of the seal which is obtained and that abrasions sometimes do occur during manufacturing and handling operations.

In accordance with the present invention, a split ring 17 is nested in the groove 15. This split ring has a larger external diameter than that of sealing portion 13 and thus the ring extends outward slightly beyond the outer edge of portion 13. Thus, if the plug is dropped, struck with a tool or otherwise mishandled, the split ring serves to protect the edge of the sealing portion against damage which might otherwise result. In the preferred embodiment shown, the split ring may either be left in place or removed at the time the plug is assembled to the engine, preferably the former. In this regard, it is advantageous that the diameter of the ring he not so large that it contact the engine block when the plug is assembled since this would require removal of the ring prior to assembly in order to assure intimate sealing contact between portion 13 and tapered surface 11. For other embodiments of the invention as where the groove is located deep within the bore 7 when the plug is in its assembled position such that the ring cannot be accommodated, it is essential that the ring he removed prior to plug installation.

The advantage to leaving the ring '17 in'place when the plug is installed is that it then remains to protect the sealing portion at such times as the plug is removed for reconditioning, gap setting or the like.

In the manufacture of spark plugs in accordance with the invention, it is most advantageous to insert the protective ring 17 in the groove of the spark plug shell immediately following the operation wherein the shell is formed with portion 13 and groove 15 as by conventional machining operations. Thus, during all subsequent conveyance and handling operations of the shell and during all subsequent assembly operations such as those wherein the insulator-centerwire assembly 5 is secured within the shell and the ground electrode welded to the shell, the smooth machined sealing portion 13 is at all times protected against nicks, scratches or the like which might otherwise occur.

' for the split ring; however, metal or other heat resistant material is preferred so that the ring can be left in place when the plug is installed without subsequent deterioration.

It is to be understood that, although the invention has been described with specific reference to a particular embodiment thereof, it is' not to be so limited since changes and alterations therein may be made which are within,

the full and intended scope of the claims which follow.

What is claimed is: p 1. A spark plug comprising a shell havinga threaded portion at its lower end, a tapered annular sealing edge portion above said threaded portion, an annular groove immediately above said sealing portion, and a split metal ringin said groove having an external diameter greater than the diameter of said sealing portion to thereby protect said portion against abrasion during handling of said spark plug.

2. A spark plug comprising a shell havinga threaded I portion at its lower end for interconnection with the cylinder head of an internal combustion engine, a resilient tapered annular sealing edge portion provided on said shell above said threaded portion, said sealing portion being adapted to be elastically deflected upon installation of said plug within the engine, a groove in said shell immediately above said sealing portion, and a split metal ring in said groove having an external diameter greater than the diameter of said sealing portion to thereby protect said portion against abrasion during handling of said spark plug.

3. In a spark plug having a shell adapted for threaded interconnection with an engine having a conical seating surface for cooperation with said spark plug to form a seal therewith, the improvement comprising an annular seating portion formed on said shell and having a tapered sealing surface, a groove in said shell adjacent said seating portion to enable said seating portion to cooperate with the engine seating surface as a cantilever spring like member having a small surface area of con tact therewith, and a split metal ring in said groove having an external diameter greater than the diameter of said seating portion to thereby protect said portion against abrasion during handling of said spark plug.

References Cited in the file of this patent UNITED STATES PATENTS 1,200,607 Graham Oct. 10, 1911 1,286,384 Mezger Dec. 3, 1918 7 2,375,822 Rose May 15, 1945 2,409,795 Rabbezzana Oct. 22, 1946 2,478,087 Bychinsky Aug. 2, 1949 2,589,338 Candelise Mar. 18, 1952 

